Do you know anything at all about Robert Weston? Maybe his marriage or death information, his children (if any) or his known address(es) or occupation(s)? I only ask because at the moment anyone who reads this and would otherwise want to help you with your question has no information at all to go on.
If you know his marriage details the best bet would be to order his marriage certificate, which would give his father's name and occupation, or else try to find the marriage in the IGI or other free index. Alternatively censuses may show your Robert living with a relative other than his wife and kids as an adult and this relative may then be a clue as to which Robert is your. Apologies if you have already tried those options.